Process for the preparation of crystalline vinylaromatic polymers with a predominately syndiotactic structure

Abstract

Process for the preparation of crystalline vinylaromatic polymers with a predominantly syndiotactic structure which comprises polymerizing the vinylaromatic monomers, alone or mixed with at least another copolymerizable ethylenically unsaturated monomer, in the presence of a catalytic system essentially consisting of: a) an adduct between a derivative of titanium having the formula R 1 R 2 R 3 R 4 Ti and a calix-[n]-arene, or an oxa-calix-[n]-arene; b) a co-catalyst selected from an alkylalumoxane and a compound of boron having the formula (II): BX.sub.1 X.sub.2 X.sub.3 or its salt.

What is claimed is: 
     
       1. A process for the preparation of crystalline vinylaromatic polymers with a predominantly syndiotactic structure which comprises polymerizing vinylaromatic monomers, alone or mixed with at least another copolymerizable ethylenically unsaturated monomer, in the presence of a catalytic system consisting essentially of: a) an adduct between a derivative of titanium having the formula R 1  R 2  R 3  R 4  Ti and a calix-[n]-arene, or an oxa-calix-[n]-arene, having formula (I): ##STR5## wherein R 1 ,R 2 , R 3  and R 4 , the same or different, represent a halogen, a C 1  -C 4  alkyl radical, a C 1  -C 4  (iso)alkoxylic radical, a cyclopentadienyl group or a dialkylamino group in which the alkyl radical contains from 1 to 4 carbon atoms;   R represents a halogen, or a C 1  -C 4  (iso)alkyl radical, X is selected from bifunctional --CY 1  Y 2  -- or --CY 1  Y 2  --O--CY 1  Y 2  -- radicals in which the substituents Y 1  and Y 2 , the same or different, represent a hydrogen atom, a methyl or a phenyl group, n is an integer between 3 and 8;   b) a co-catalyst selected from an alkylalumoxane and a compound of boron having the formula (II):   BX.sub.1 X.sub.2 X.sub.3                                   (II)       or its salt, wherein X 1 , X 2  and X 3 , the same or different, represent a C 1  -C 20  fluorinated hydrocarbon radical.   
     
     
       2. The process according to claim 1, wherein the molar ratio between vinylaromatic monomer and titanium is between 1,000 and 200,000. 
     
     
       3. The process according to claim 1, wherein the co-catalyst is used in such quantities that the molar ratios of aluminum/titanium and boron/titanium are respectively in the range of from 50 to 1000 and of from 0.5 to 5. 
     
     
       4. The process according to claim 1, wherein the catalytic system described above comprises an aluminium alkyl wherein the alkyl group contains from 1 to 6 carbon atoms. 
     
     
       5. The process according to claim 4, wherein the molar ratio aluminium alkyl/titanium is between 0 and 1,000. 
     
     
       6. The process according to claim 1, wherein the polymerization reaction is carried out in mass or in solvent. 
     
     
       7. The process according to claim 6, wherein the solvent is used in such quantities that the ratio by volume solvent/monomers is between 0 and 10. 
     
     
       8. The process according to claim 1, wherein the polymerization is carried out at temperatures of between 20 and 100° C.